Aggressive behavior in Preschool Hens

Our co-op preschool has two young hens that have been laying for 3 months now. We've been having problems with them pecking at feet & legs (parents & children) & they have also pecked at children's faces. My school job is taking care of the animals, so I've been mediating parent-kid-chicken trouble for the past 2 months. Before this summer I hadn't had any experience raising chickens.
One is a Rhode Island Red & the other an Ameraucana, they are big healthy birds with a 5 x 8 barn space, 3 laying boxes all to themselves & the straw is changed daily. They have fresh water & laying crumble food inside the barn & can freely pass from barn to playground. The school has had chickens for several years, but never any this young, & chicken aggression hasn't ever been a problem before. Their wings are clipped. They are free to roam the play yard from 9-3 M-F & depending on the weekend work parent may get a hour or two outside over the weekends. We haven't noticed more pecking after being cooped up all weekend, so I'm not sure if their outside time is a factor or not. We're located in Northern California & a local told me all the little earthquakes we've been having might get the birds riled up.
Just to be contradictory, the chickens have been hand raised & can be very approachable, they stop & seem to be asking me to pet their backs (I raised them for school this past summer). The chickens are very easy for most parents to pick up. The teachers say these are the sweetest hens school has ever had, but on the flip side they are the most aggressive & have attacked kids' faces. Obviously we need birds that can safely share a yard with 24 kids, so I'm looking for any advice on how to curb their aggressive behavior & pecking.
The Ameraucana pecked a little boy near the eye (breaking the skin) before winter break, has flown aggressively towards parents & kids & occasionally chases kids away. The Rhode Island Red seems to have more trouble with pecking & chasing. She will peck at feet & many parents thought, probably correctly, that she was asking for chicken scratch to be tossed & then they would feed her. My theory is that this got her into a bad habit & I let all of the parents know they are not to fed the hens if they peck at their feet. It does seem to be getting a little better.
Yesterday a hen (still waiting to hear back which one) pecked a little girl pretty badly on the nose, the child was sitting down & coaxing the chicken to come to her. Since we've been having chicken problems we've been trying redirect kids away from the birds if they want to be near them, but of course some kids love animals & will try to visit them anyway.
At the beginning of the year we did have problems with some kids breaking the chicken rules (no chasing, no picking up, no rough stuff, no hand feeding) & we have reined in the rougher kids. So now the chickens aren't being bothered, but are still being aggressive, chasing kids & parents around. I'm worried they have been conditioned to be on the defensive, so we parents are working to give them lots of space on the playground. We've also been putting the hens back in the barn if they are being aggressive.
Since there have been a couple of face pecking incidents I'm beginning to consider beak clipping their top beak (yes debeaking, but not as severe as some of the photos I've seen online). I'm also going to get some fake eggs for their nesting boxes, I've heard that can calm them down.
I've always loved that my kids' school to has pets & chickens running around in the play yard (it even inspired me to build a coop & now I have 3 young hens at home), but we can't have aggressive birds attacking preschoolers. Thanks for your advice!

First, I love that your school has chickens! But, honestly, a lot of times chickens and small kids don't mix well. RIR in particular are a known aggressive breed. My chickens know me very well, but they peck at my feet, legs, and face too. I've been pecked in each eye. I don't sit down and let them jump on my shoulders anymore. They're not necessarily being mean- more like being curious. But they can really hurt. Is there any way to build them a nice, large run so they can't get to the kids? It might be a happy medium between other kids getting maybe even more seriously injured and keeping these hens.
I hope someone has some answers for you.

Interesting problem. I am pretty sure the birds were conditioned to act the way they are. Unfortunately, breaking them of these undesirable behaviors is going to be very challenging. The birds need to be kept away from the children at this point because they are going to hurt someone. It is not a great idea to have chickens and children running around in the same space without very close supervision anyways. Too much chance of someone getting hurt- probably the chickens up until this point, but the chickens have learned how to fight back, so from this point on the children are going to be the ones getting hurt. These birds may be a lost cause in this setting. They have been trained that if they peck at people they will receive a food reward for it. Or if they are being made uncomfortable a jab to someone's face will stop it. It may not have been intentional training, but that's how it is perceived by the birds, so for all intents and purposes that's what it is. Chickens are not rocket scientists, so they may never be able to be broken of these nasty little habits.

Chickens are flock animals that, in the absence of a real flock, will grab on to a group of familiar creatures and view them as their flock. Unfortunately, chickens are also very reptilian in nature and have a flock structure that is quite brutal and unforgiving. Chickens don't mix well with children. They will not hesitate to attack a child for some perceived threat or weakness. Children they view as members of their flock will be especially targeted.

If you decide to try some new chickens in this setting I would forbid the participants of your program from feeding the birds. The birds can wander around as eye candy but don't need to be held, coddled, physically molested in any way or fed outside their regular feed stations. The birds will be naturally standoffish, but may tolerate some occasional touching. The point being that they are not likely to view the children as flock members to be chastened when the chickens want to improve their standing in the pecking order. Treating the birds more like the farm animals they are and less like a school's pampered pets will likely make for a better situation for the children. I would still firmly recommend that the chickens are kept separately in a securely fenced area away from the children for everyone's safety.